1. Field of the Invention
This invention relates to a leaf spring for various industrial fields, and more particularly to a new type of leaf spring which is efficient in maintaining the health of the human body.
2. Description of Background and Material Information
Although various types of leaf springs are used in the machine industry including applications found in the furniture industry, there has been very little development of leaf springs designed to enhance or maintain human health. In the past, the natural power of leaf springs was primarily used to proide a comfortable feeling as a result of its resiliency. One example of such a conventional use of a leaf spring is Japanese Utility Model Laid-Open No. 55-100,565 (the Japanese Utility Model Application No. 53-182,991) which shows a plurality of sliced wooden plates overlapped to each other to cause their central parts to be bent into an arch form with fibre reinforced plastics (FRPs) covered on both upper and lower surfaces of the plates (hereinafter referred to as prior art). This prior art shows only a cross sectional shape of the plate, does not describe any physical property, and it is not possible to understand at all from the description whether the spring is practically applied, or if there is any relationship of the spring to the human body at all. This prior art does not appear to be actually applied practical technology.
Another use of the leaf spring is in bedding applications. Related to this, it is well known that the rational attitude of the human body during sleeping is near to the right attitude of the human body during standing. Notwithstanding this fact, however, the conventional type of beds for the most part include some coiled springs, which prevent a rational attitude of the human body from being obtained.